1. Field of the Invention
The present invention relates to a method of manufacturing a nozzle plate, and more particularly, to a method of manufacturing a nozzle plate having a nozzle of a cross-sectional shape which is formed by combining a tapered section and a straight section.
2. Description of the Related Art
An inkjet recording apparatus (inkjet printer) is known which forms a desired image on a recording medium by ejecting ink droplets from nozzles toward a recording medium, while causing a print head including a nozzle plate having a plurality of nozzles on an ejection surface opposing the recording medium to move relatively with respect to the recording medium.
In a print head of this kind, if dimensional accuracy is poor in terms of the shape and position of the nozzles formed in the nozzle plate, or the like, then variations occur in the size (volume) of the ink droplets, their direction of flight and their speed of flight. Consequently, image deterioration may occur and the ink ejection efficiency may decline. Therefore, various methods of manufacturing a nozzle plate have been proposed in order to resolve this problem (see, for example, Japanese Patent Application Publication No. 2001-329392, Japanese Patent Application Publication No. 5-193144, Japanese Patent Application Publication No. 2002-154210 and Japanese Patent Application Publication No. 10-166595.)
Japanese Patent Application Publication No. 2001-329392 discloses a method of manufacturing a nozzle plate where tapered nozzles are formed by forming a taper-shaped electroforming mold by light exposure using diffused light, in order to stabilize the position of the ink meniscus and suppress the loss of ejection energy.
Japanese Patent Application Publication No. 5-193144 discloses a method of manufacturing a nozzle plate in order to stabilize the ink ejection direction. In the method, a member having guaranteed nozzle diameters formed by pressing a metal is obtained, a photosensitive dry film is laminated thereon, and light exposure with scattered light is performed from the metal side, thereby forming nozzles in which the metal side has a straight shape and the dry film side has a tapered shape.
Japanese Patent Application Publication No. 2002-154210 discloses a method of manufacturing a nozzle plate in order to stabilize the ejection direction of very fine ink droplets. In the method, a photosensitive resin is exposed in a straight shape by using a normal mask, and the photosensitive resin is then exposed using a graduated mask having a light transmissivity that changes gradually rather than being uniform. When the resin is developed, nozzles are obtained in which the ink inlet side has a curved shape and the outlet side has a straight shape.
Japanese Patent Application Publication No. 10-166595 discloses a method of manufacturing a nozzle plate, in order to stabilize the ink ejection direction. In the method, resist is coated onto the entire surface of a nozzle forming member in which nozzles having an overhang shape have been formed, exposure and development are carried out from the ejection surface side, and electroforming is carried out from the opposite side (ink supply side), thereby forming nozzles having a substantially cylindrical shape (or a substantially circular conic/trapezoid shape).
However, there are problems of the following kinds in the above methods of manufacturing nozzle plates.
In the method disclosed in Japanese Patent Application Publication No. 2001-329392, there is no straight section in the nozzles and the ink ejection direction is not stable. Furthermore, since a tapered electroforming mold is used, then if there is variation in the thickness of the electroforming film, albeit a very slight variation, this could cause variation in the nozzle diameters, and hence lead to a decline in ejection efficiency.
In the method disclosed in Japanese Patent Application Publication No. 5-193144, resin material (dry film) is disposed on the ink flow channel side, and there is a possibility that problems with the resistance to ink may arise.
In the method disclosed in Japanese Patent Application Publication No. 2002-154210, since exposure steps are required to be performed twice, positional displacement can readily occur between the steps, leading to a decline in the dimensional accuracy of the nozzles, which in turn causes a decline in the ejection efficiency and fluctuation in the ejection direction.
In the method disclosed in Japanese Patent Application Publication No. 10-166595, since the nozzles have an overhang shape, variation in the nozzle diameter is liable to occur and it is difficult to stabilize the ink ejection direction.